Utilizing the AR platform as a LRH weapon system is valid in my opinion. I have the original Armalite AR10T in .308 that I've had for a while, and supplemented it with the 10T upper in .243 Win. I have taken quite a bit of long range animals with both, but the majority with the .243 Win. Both uppers are capable of less than 1/2 MOA with handloads.

I got the .308 from my BIL who was an LEO sniper. He wanted to go with the AI bolt for his duty weapon. He is kicking himself for selling me his rifle. I make a point to show him some of the groups I've shot with it. It's a heavy system, but for now, I could care less.